CA1113646A

CA1113646A - Vinyl polymerization with boron chelates as catalyst and photoconductive sensitizer

Info

Publication number: CA1113646A
Application number: CA289,677A
Authority: CA
Inventors: James M. Halm
Original assignee: AB Dick Co
Current assignee: AB Dick Co
Priority date: 1976-11-08
Filing date: 1977-10-27
Publication date: 1981-12-01
Also published as: DE2759809C2; GB1584879A; US4153769A; GB1584880A; DE2749768A1; DE2749768C2; JPS5358591A

Abstract

ABSTRACT OF THE DISCLOSURE
The preparation of a photoconductor which comprises the polymerization reaction product of an N-alkenyl carbazole or derivative thereof such as N-vinyl carbazole, in the presence of a catalyst in the form of a monochelate or multi-chelate of boron in which the chelate catalyzes the polymerization reaction and remains in the polymerization product as a sensitizer for the photoconductive properties of the organic polymer.

Description

3~

S P E C :[ r~ c A q' I 0 N

This invention relates to the polymerization o~
vinyl monomers to form homopolymers and copolymers ancl particu-larly vinyl carbazoles and derivatives thereof with boron che-lates and to photoconductive comFIositions and elements produced therewith.
Poly-N-vinyl carbazoles and derivatives thereof are substances ~idely used as organic photoconductors in the prepara-tion of electrostatic photoconductive elements from which multi-ple copies can be produced in the duplicating field. By them-selves, the poly-N-vinyl carbazoles and derivatives are not sufficiently photoconductive unless modified by the presence of varying amounts of acceptor type compounds, such as fluorenone derivatives, phthalic anhydride derivatives, halogenanil deriva-tives or ketone derivatives. In practice, the electron affini-tive compound (acceptor compound) is blended with the polymerafter polymerization of the carbazole monomers.
N-vinyl carbazole and its derivatives polymerize very slowly in the absence of a polymerization catalyst. For pur-poses of accelerating polymerization use has been made of a cata-lyst such as ditertiary butyl peroxide, azobisbutyronitrile,betanaphthol, monoethyl aluminum dichloride, and the like. The presence of such catalysts in the polymer often presents problems in the subsequent formation of the charge transfer complex or interferes in other ways with the selected acceptor. As a ~5 result, it has been the common practice to remove the catalyst from the polymer before formulating the polymer with the desired :. ~
electron affinitive compound, if the polymer is to be used ~`~ as a photoconductor. Such separation steps are costly and time consuming and thus introduce a barrier to the commercial acceptance oE photoconductive elements fabricated of such organic photoconductors.

: , It is an object of this illVent:iOIl to providc a method -for proclucing a polyalkenyl-c.lrbazole arlcl derivatives thereof, such as poly-N-vinyl carbazole, by polymerization of tlle monomer in the presence of a catalytic agent which is sufficiently electro-negative to result in a photoconductive ; material whicil can be used in the preparation of photoconductive elements, and it is a related o~ject to produce and to provide a method for producing new and novel ketonate compounds which find utility in the po]ymerization to produce new and improved photoconductive polymers of alkenyl carbazoles and derivatives thereof.
It has been found, in accordance with the practice of this invention, that a class of compounds, heretofore referred to as initiators, are effective to catalyze the polymerization of vinyl based polymers and copolymers, particularly alkenyl carbazoles and derivatives thereof, and more particularly N-vinyl carbazole, wherein the resulting polymerization products are sufficiently electro-negative to enable the catalytic component to remain in the formed polymer composition to product an organic photoconductive material in which a high degree of photoconductivity may be achieved by comparison with the mere blend of the catalyst compound with a polymerized N-vinyl-carbazole. The new class of compounds have the following general formula:

(Y)n~ R2 C O
' / \ (1) ` ~- C BZ
! ~ / 2 ~X)n ~ Rl - C--O
in which X and Y may be the same or different and represented by a halogen ; or an alkyl or cyclo aliphatic group preferably having from 1 to 10 carbon atoms, such as methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, -, ~.i ~

.

isobutyl, cy~lobutyl, pcntyJ ~Incl the I:ike, or all aryl or alkaryl group, sucll as phenyl, tolyl, anth:r.lcyl and the like, and an alkoxy group, such as metlloxy, ethoxy and the like, or halogena-ted methyl derivative, such as methyl chloride; Z is an aryl group such as phenyl or a halogen group such as chloro, but preferably fluoro, n is a number of from 1 to 5 and Rl and R2 may be the same or different, and are represented by an alkyl or cyclo aliphatic group having from 1 to 10 carbon atoms as defined above, or an aryl or alkaryl group as defined above. Included are the group of compounds in which R2 is represented by the group having the general formula:

: lo ~ - ! c c~l = C - R - ~Y) ~ (2) O O

\ BFz J
p in which Rl has the same meaning as defined above and _ is a number of from 1 to 2.
The following structural ormulae illustrate preferred initiator ~ compounds produced in accordance with the practice of this invention and : embraced w thin the above structural formulae:
., ~ ~ ~ J H-C / BF (3) ~_ \C-o/

C = O (4) CH ~C o/ 2 .' J, . .
, ~ ' . . .
, ` .

~3 / \
C=0~ / \ ~5 H-¢ ~--~
~'~C-0~ ~ ~/ 2 . 5 :`
C}~30 ~(~C-- 0 C~ ~ /~P2 ~6) '~ ' ~H~30 ~)_ C= 0 ~ ~BF2 F ~ C--0 `
~BF~

c~ C~

;C-CI~-IC_~ ~6 ~F2 ~CH--C~}O~}i3 CH~C--J~>~H3 O BF~ -~
, ~
~ 30 : ~
''" , : ~
~ ' ' . , . , , . . . - .~ `

3~
.

C// Cl~ - \C ~ 2~5 ~f~ 0~
,; I ~ I ~
CH ~ C2H5 ; - BF2 ,r, ; In the practice of this invention, the initiator is ;? intimately mixed with the carbazole monomer and then heated s lO until fusion of the mixture occurs, while in an inert atmos-phere such as a blanket of nitrogen. The mixture is heated for reaction at a temperature generally within the range of 65-160C, with agitation.
The amount of initiator used to catalyze the poly-merization reaction will depend somewhat upon the reaction temperature, the individual components reacted, the amount desired in the final product, and the solubility of the ini-tiator in the melt. A desirable effect is achieved when use r~, is made of the initiator in an amount of 0.5% by weight of the monomer. Beneficial use is derived from additional amounts of initiator but it is undesirable to make use of an amount .~ which exceeds 20% by weight of the monomer. In practice, it is preferred to make use of initiator in an amount within the range of 1.0 to 4.0% by weight of the monomer. Within this range, the desired amount of polymerization can be achieved at temperatures within the range of 60-200C. For example, with 1.5% by weight catalyst, polymerlzation is completed in 30 minutes at 80C and with 3.0% by weight catalyst, polymeri- -.~ zation is completed in 15 minutes at 80C.
3 Polymerization by an amount suitable for use in the ~, ~ 5 -:... ' . .

~ 3~;>~3 preparation o~ photoconcl~lctive coatings is inclicated by increase in viscosity o~ the ~el~ and/or by an abrupt darkening of the melt which normally coincides with increase in viscosi-ty or solidification of -the reaction mass.
The polymerization reac-tion mass can be -ta~en up in a solvent, such as hot tetrahydrofuran, to form a coating eom-position which can be applied to a suitable substrate, prefer-ably a conductive substrate paper, metal, plastics and the like, as by dip eoating, draw rod coating or the like, followed by drying and preferably curing at elevated temperature. Coatings having a thickness of 3 to 12 mierons are suff~eient and it will ; be seen that the eoating strongly bonds to the surfaee of the substrate, Multi-ehelates, as represented by the struetural formula (21 and illustrated by the formulae (6) to (8? ! are believed to be new and novel eompounds whieh have not hereto-fore been produeed and their use as eatalysts in the polymeriza-tion of N-vinyl earbazoles and derivatives thereof in the pro duetion of new and improved photocondueti~e materials is also believed to be new-.
Sueh multi-ehelates ean be produeed, in aeeordanee `~ with the praetice of this invention, by reaetion of the appro-priate ligand with a BF3 etherate, as illustrated by the follow-; ing examples~

- a) Preparation of ligand, ` The ligand is first prepared by a Cross Claisen con-: densation reaetion of dimethyl terephthalate with a 4'-ethyl-aeetophenone in aeeordanee with the following equation ~ ' , .
.: .

C_CH2- H C - CEI2C ~I~CE~2-~
~_C/~ > (~ [~

2 5 2 5 H5 ;. .
~ ~ ( 11 ) , , A 200 ml portion of dimethyl sulfoxide is placed ,' over 15 grams of sodium hydride (50% in oil~ and the mixture is stirred for about one-half hour. Approximately 0.2 mol (39 g) of dimethyl terephthalate is added to the sodium hydride and the mixture stirred for about one-half hour under a nitrogen ; atmosphere which is maintained by passing nitrogen through a ~.
bobbler. A portion of 0.4 mol (59 g) of 4'-ethylacetophenone is added to an equal volume of dimethyl sulfoxide and the solu-tion is added dropwise, from a dropping funnel, to the stirred mixture of sodium hydride and acetone. An ice water bath is `~ used to control the temperature of the reaction mixture when it begins to foam and reflux due to the exothermic reaction.
~ 2~ After completion of the addition of ketone, the mlxture is `~ stirred at room temperature for 5 hours. The red mixture is poured into a beaker (1 liter) half filled with ice and con-taining 100 ml of concentrated HCl. The yellow precipitate is isolated by filtration and dissolved in 400 ml CH2C12. The CH2C12 solution is evaporated on a steam bath to one-third its original volume and the solution placed in a freezer at ` about -10C over night.
The yellow solid from the crystallization was used in the preparation of the boron chelate.

3 : ~ -... .

~ - 7 -b) Preparatiorl of che]ate.
The chelatecl compound was obtained by reaction of the tetraketone ligand wi-th BF3 ethera-te in accordance with the following equation:
BF
~0 ~ ~ C El C-C~=C- ~ - C~H5 cr_ CH2 -- C-~ ~ ~I~
2 BF3 -~¦ ¦ ~ 2 O I (glyme ) ~ ,~
~ r~solven~ C}I-Ç~ 12) 10~ - CH2 ~ 2Hs(d m~thoXY- ~ ~ \

20 grams (0.048 mol) of the ketone was added to about 2Q0 ml of 1,2-dimethoxyethane solvent and the mixture was stirred under a nitrogen atmosphere. The mixture was brought to about 50C and 12.6 grams of a 50~ BF3 (as the ethyl etherate~ (0.096 mol) was added to the mixture. The suspension was refluxed for 4 hours, cooled and then filtered.
The yellow-orange solid was re-crystallized from hot acetone as fractions from a Soxhlet extractor. The third frac-tion, after about 48 individual extractions of the solid, was taken for analysis as product and used for the catalysis reac-tion and as a blend sensitizer in the formed polymerization product.
~5 EXAMPLE 2 ~
~ In the preparation of the dichelate, represented by ~ -; the formula (7), the 4-ethylacetoxyphenone in Example l was replaced by an equal amount of 4'-methylacetophenone.
EXAPqPLE 3 3 In the preparation of the compound represented by ~.' ' .
' .
. ~ . , "
the formula (6), Exam~le 1 was followed exceo-t that the ~'-ethyl-ace-tophenone was substitu-tecl by an equivalent amount of aceto-phenone.
The following examples, whicn are given by way of ~ 5 illustration, and not by way of limitation, demonstrate the use t~ of the boron chelates as catalysts in the polymeriæatlon of s' N-vinylcarbazole and derivatives for the preparation of organic polymers having improved photoconductive characteris-tics.
E ~LE 4 10 grams of N-vinylcarbazole are thoroughly mixed with 0.3 gram of the compound represented by the formula (5) f and placed in a flask containing a stirrer button. The flask is ; flushed out with a nitrogen stream for 10 minutes and a nitrogen atmosphere is maintained by continued bubbling of nitrogen there-~ 15 through. The flask is heated until the mixture melts at a tem-; perature of about 60-65C. Polymerization is continued for 10 `~ minutes with corresponding increase in viscosity and resultant ; color change from a yellow to a deep amber. The mass quickly solidifies. The reaction mass is extracted with hot tetra-hydrofuran (THF), a slight residue filtered off, and the volume of solution adjusted to 100 ml with THF.
The solution is coated onto an aluminum substrate with a draw rod. The tough adhesive film, formed upon drying, was transparent and had high photopic transmission. Its electro-photoconductive properties, when illuminated from a tungsten lightsource, were as follows:
1. positive charge acceptance = 460 volts, dark decay =
1.9 volts/sec., exposure required to tl/3 of the decay curve =
330 ~j/cm , residual volkage = 50 volts.
3 2. negative charge acceptance = 600 volts, dark decay =

,: _ g _ ~ 36~

1.7 volts/sec., exposure required -to tl/3 of the deca~ curve =
360 ~j/cm , residual voltage = 40 volts.

The same procedure was carried out with the same sub-stances as in Example 4 except that the ratio of initiator/
monomer = 0.9 g/10 g. The melt solidified in a few seconds.
A drawbar coating from 100 ml of THF gave the following electro-photoconductive properties when :illuminated by a tunysten light source:
1. positive charge acceptance = 500 volts, dark decay =
16.6 volts/sec., exposure required to tl/3 of the decay curve =
144 ~j/cm , residual voltage = 50 volts.
2. negative charge acceptance = 550 volts, dark decay =
, i,`~ 8 volts/sec., exposure to tl/3 of the decay curve = 187 ~j/cm2 , residual voltage - 30 volts.
The THF was evaporated off from the solution of Example 4, and mixed solvent THF/cyclohesanone = 40/60 (%) was used as the coating solvent. With the use of either solvent, the coating was transparent and of high photopic transmission. From the mixed solvent, the electrophotoconductive properties of a draw-bar coating, with tungsten illumination, were:
1, positive charge acceptance = 400 volts, dark decay =
18 volts/sec., exposure required to tl/3 of the decay curve =
,~ 216 ~j/cm2 , residual voltage = 30 volts.
2. negative charge acceptance = 400 volts, dark decay =
19 volts/sec., exposure to tl/3 of the decay curve = 291 ~j/cm2, residual voltage - 30 volts.

The procedure of Example 4 was followed except that 3 the compound (5) was replaced with the compound represented by . ..

3~;~6 the formula (6), ancl the ratio of initiator/mono~er = 0,3g/lQg, The melt solidified after about 15 minutes at ~QC, The reactlon mass was extractecl into the TIIF ancl the Einal solution was diluted to 100 ml in a solvent system of 60/40 THF/cyclohexanone.
A tough transparent film with excellent adhesion on an aluminum substrate was obtained~ The film, with high photoplc transmis-sion, had the follo~ing electrophotographic properties:
1, positive charge acceptance = 42Q volts, dark decay =
1 Yolt~sec~ exposure requlred to tl/3 of the decay curVe =

396 ~j/cm , residual voltage = 3Q volts~
2. negative charge acceptance = 41a volts, dark decay =
1 volt/sec., exposure requlred to tl/3 of the decay curve =
48Q ~j/cm ~ residual voltage = 4Q volts.
~ ~eadable copy was made from th;s photoconductive plate from a commercial copy machtne using negative corona~

The procedure of Example 4 was followed except that use was made of the initiator represented by the formula (7) in the ratio initiator/monomer = 0.15g/5.0g. Polymerization took place about 10 minutes after the mixture melted with the ; temperature near 80C. The reaction product, dissolved in THF, was coated onto an aluminum substrate and formed a tough adhesive, transparent film. The electrophotographic properties of this coating, with the use of tungsten illumination, were:
1. positive charge acceptance = 500 volts, dark decay =
6.6 volts/sec., exposure to tl/3 of the decay curve = 2205 ~j/cm~, residual voltage = 100 volts.
2. negative charge acceptance = 650 volts, dark decay =

4 volts/sec., exposure to tl/3 of the decay curve = 2200 ~j/cm , 3 residual voltage = 40 volts.

.

.~

~3~

E~AMPLE 8 The procedure of Example 4 was followed except that the initiator was the compound represented by formula (9) with the ratio init~ator/monomer = 0.4g/lOg The melt polymerized aftex about 10 minutes at 80C. The reaction mass was extracted into hot THF and the volume concentrated to 100 ml. The parti-culate matter w~s filtered off and the solution coated onto an ~ aluminum substrate A tough, adhesive, transparent film o~
high photopic transmission was obta~ned having the following electrophotographic properties toward tungsten illumination:
` 1~ positive charge acceptance = 85Q volts, dark decay =
; 3 volts/sec., exposure required to tl/3 of the decay curve - -141 ~i~cm , residual voltage = 5a volts, 2~ negative charge acceptance = 7gO voltsl dark decay =
1 volt~sec~ ! exposure to tl/3 of the decay curVe = 206 ~j/cm residual voltage - 5Q volts~
LXA~LE 9 ;~ The procedure of Example 8 was repeated with the same substances but in the ratio initiato~/monomer = 0.8g/lOg. The reaction mass polymerized in a few seconds after the melt formed.
The THF coating on an aluminum substrate exhibited the physical properties as in Example 8. The electrophotographic properties of this coating toward tungsten illumination were:
1. positive charge acceptance = 650 volts, dark decay =
6 volts/sec., exposure required to tl/3 of the decay curve =
91 ~j/cm , residual voltage = 50 voltsO
2. negative charge acceptance = 700 volts, dark decay =

3 volts/sec., exposure to tl/3 of the decay curve = 139 ~j/cm ' residual voltage = 50 volts.

When an 80B filter was used to simulate more of a daylight :

' . .

'~:

~3~;~fL6 fluorescent quality, t~le electrlcal properties were:
1. positive charge acceptance - 600 volts, dark decay =
6 volts/sec., exposure to tl/3 of the decay curve = 81 ~j/cm2, residual voltage = 50 volts.
2. negative charge acceptance = 650 volts, dark decay =
4 volts/sec., exposure to tl/3 of the decay curve = 181 ~j/cm2, residual voltage = 50 volts.
Excellent line copy was obtained when a plate coated with this polymerization formulation was used in a commercial copy machine employing positive corona.

The compound utilized as an initiator in Example 9 is only slightly soluble in typical coating solvents. To estab-; lish the effects of blending vs. those obtained in a polymeriza tion coating, 0.8 g of compound (9) was used in one case as the ,-:
initiator of n-vinyl-carbazole polymerization, and in the other as simply the acceptor in a polyvinylcarbazole formulation.
For the blending formulation, the acceptor was roller milled with a THF solution containing 10 g of commercial polyvinyl-carbazole. The mixture, after two days, was filtered and coated - onto an identical substrate as was the polymerization formula-tion of Example 9. The physical properties were essentially the same in either case. A comparison of the electrophoto-graphic properties is given below:
2~ charge acceptance dark decay exposure t~ residual (volts) (volts/sec) tl/3 ~J/cm voltage _ ._. . .__ 10% polyvinyl- + 480 1 220 35 carbazole blend - 410 1 270 30 Polymerized N-vinyl + 650 91 50 carbazole with ~9) - 700 3 139 50 3~ _ __ -' ~ , These clata sho~ that the polyrnerization process involving the initiator-acceptor compound provi~es a coating formulation which is about ~hree times as fast toward positive corona as the blending formulation.

The procedure of Example 4 was followed using the initiator (10) and the monomer N-vinylcarbaz~le in the ratio initiator/monomer = l.Og/lOg. The polymerization occurred about two seconds after the mixture melted. ~ filtered 100 ml ~0 of the reaction products gave a tough transparent coating of high photopic transmission. Its electrophotographic properties toward tungsten illumination were:
1. positive charge acceptance = 500 volts, dark decay =
4 volts/sec., exposure required to tl/3 of the decay curve =
105 ~j/cm2, residual voltage = 50 volts.
2. Negative charge acceptance = 650 volts, dark decay =
4 volts/sec., exposure required to tl/3 of the decay curve =
228 ~j/cm2, residual voltage = 40 volts.

Positive corona in a commercial copy machine was used to make ~; 20 several copies from a plate coated with this formulation.

EX~lP~E 12 The procedure of Example 4 was followed using the initiator (8) and the monomer N-vinylcarbazole in the ratio ... .
, ~,! initiator/monomer = O.~g/lOg. The polymerization occurred about ten minutes after the mixture melted. The reaction mixture was taken up in THF, filtered~ and coated onto an aluminum substrate. The light yellow coating had good adhesion and very high photopic transmission. A solution blend of this acceptor and polyvinylcarbazole could not be prepared due to ` 3 the high insolubility of the acceptor compound. The fact that ,:

'':

the polymerization mlxt~lr~ shows photoconductivity of moderate measure indicates a different mechanism in the photoconduction between the polymerization reac-tion products and the charge transfer products from blending. The electrophotographic pro-perties of the coating from the N--vinylcarbazole polymeriza-tion, using tungsten illumination, were:
1. positive charge acceptance = 650 volts, dark decay =
6.6 volts/sec., exposure required to tl/3 oE the decay curve =
950 ~j/cm2, residual voltage = 60 volts.

2. negative charge acceptance = 600 volts, dark decay =
10 volts/sec., exposure required to tl/3 of the decay curve =
917 yj/cm2, residual voltage = 50 volts.
The exposure to tl/3, with the use of the 8OB filter, required 100 ~j/cm less than the above values.
; 15 EXAMPLE 13 In order to tes~ the effect on the polymerization of N-vinylcarbazole and the photoconductivity of the possible re- -action mixture, from compounds in these classes having auxiliary ligands other than fluorine, compound (5) was used as the initia-tor. A 10 g portion of N-vinylcarbazole and 0.4 g of compound

(5) were intimately mixed and set up for the polymerization reaction as in Example 4. Twenty minutes after melting, and ~-- while being maintained at a temperature of about 80C, the re-action mass became viscous enough to cause the stirrer button to freeze, and a few minutes thereafter, the mass solidified.
The coating, from THF, exhibited a high photopic transmission, `~ was adhesive, tough, and had the following electrical properties toward tungsten illumination:
1. positive charge acceptance = 550 volts, dark decay =

1 30 2 volts/sec., exposure required to tl/3 of the decay curve =

2131 ~j/cm , residual voltage = 75 volts.

, ~ .
- . ~
.. .. .. .

2. negatlve charcJe acceptance - 610 volts, clark decay =
2 volts/sec., exposure required to -tl/3 of the decay curve =
1624 ~j/cm , residual voltage = 90 volts.
With an 80B filter, to simulate more of a daylight fluorescent illumination, the electrical properties were:
3. positive charge acceptance = 640 volts, dark decay =
2 volts/sec., exposure re~uired to tl/3 of the decay curve =
1279 ~j/cm2, residual voltage = 75 volts.
4. negative charge acceptance = 750 volts, dark decay =
10 2 volts~sec., exposure to tl/3 of the decay curve = 1591 ~j/cm2, residual voltage = 150 volts.

This example illustrates the catalytic effect of ~ class 1 type compounds toward non-carbazole monomers. The /-~ 15 procedure of Example 4 was followed using the compound (3) as the initiator and the monomer 4-vinylpyridine in the ratio initiator/monomer = 0.4g/lOg. The melt took on a red coloration ; and became viscous after about four hours of heating at about 130C. A coating from THF produced an extremely tough, adhesive film. The coating did not light decay.

This example illustrates the catalytic effect of ; class 11 type compounds toward non-carbazole monomers. The ~¦ procedure of Example 4 was followed using the compound (9) as the initiator and the monomer 4-vinylbiphenyl in the ratio .
initiator/monomer = 0.4g/lOg. The melt was maintained at a temperature of 130C and after about four hours became viscous.
A coating from THF produced a tough, adhesive film. The coating did not light decay.

^ I
, . ' ~ `
.~ . .

Claims

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A process for the preparation of vinyl based polymers and copolymers comprising the steps of polymerizing the vinyl based monomers in the presence of a catalyst com-pound having the general formula .
in which X and Y are selected from the group consisting of a halogen, an alkyl or cycloaliphatic group, an aryl or alkaryl group, an alkoxy group and a halogenated methyl derivative, Z
is an aryl or halogen group, n is a number from 1 to 5, R1 and R2 are selected from the group consisting of an alkyl or cyclo-aliphatic group, an aryl or alkaryl group, and in which R2 may be a group having the general formula in which R1 has the same meaning as above and p is a number from 1 to 2.

2. The process as claimed in claim 1, in which the vinyl based monomer is an N-alkenyl carbazole or derivative thereof.

3. The process as claimed in claim 2, in which the polymer and copolymers have sufficiently sensitive photoconduc-tive properties for use as an organic photoconductor.

4. A process as claimed in claim 1 or 2, in which the alkyl group or the cycloaliphatic group have from 1 to 10 carbon atoms.

5. A process as claimed in claim 1 or 2, in which the halogen is fluorine.

6. A process as claimed in claim 1 or 2, in which the catalyst component is present in an amount within the range of 0.1 to 20% by weight of the carbazole.

7. A process as claimed in claim 1 or 2, in which the polymerization reaction is carried out at a temperature within the range of 60-200°C.

8. A process as claimed in claim 1 or 2, in which the polymerization is carried out as a hot melt of the carbazole and catalyst.

9. A process as claimed in claim 1 or 2, in which the polymerization is carried out in the absence of a diluent.

10. A process as claimed in claim 1 or 2, in which the alkenyl carbazole is N-vinyl carbazole and analogs thereof.

11. A composition for use in the preparation of photoconductors com-prising the polymerization reaction product of the process of claim 1 or 2.

12. The preparation of a photoconductor comprising coating a substrate with a composition containing the polymerization reaction product of claim 1, drying the coating, and curing the coating at elevated temperature.

13. A photoconductor produced by the method of claim 12.

14. The process as claimed in claim 1 in which the catalyst has the general formula prepared from an oxalate ester.